Functional Prototyping

Prove and perfect your designs with tough, precise testing

Iterative, agile product development is the promise of advanced 3D printing. Functional prototyping with engineering thermoplastics or digital materials reveals how your next product will perform, well before you commit to production tooling.

Surrogate Components for Design, Manufacturing, Training and Support

Overview

There are times when a component’s only function is to occupy the space that it will take in the final product. Claiming this space provides assessment and verification of critical installation issues such as assembly, serviceability, routing and interfaces. It also allows assessment of product performance aspects that are adversely affected by clearance from a neighboring sub-assembly.

One evaluation option is to manufacturer or purchase the component. However, for high-value parts with complex designs, and possibly long lead times, the investment may be unwarranted and ill advised. In the time span between installation assessment and final product assembly, design modifications may occur and parts may be damaged during repeated installation cycles. If this occurs, the component must be either repaired or replaced. Another downside to use of production components is that work-inprogress (WIP) expense increases, and schedules may be delayed by late deliveries of components. This is especially critical when working on new equipment designs.

Application Outline

Mock-ups may be substituted for production components during the assembly and interface evaluation phase of a project. For simple configurations, all necessary detail can be incorporated in a machined or fabricated part that is inserted in the product assembly. However, with complex, intricate subassemblies, the mock-up may be oversimplified, which can result in an oversight of installation and interface problems.

Surrogate components preserve all of the critical details for an installation while minimizing expense and lead time when they are manufactured with Fused Deposition Modeling (FDM).
Produced as needed, with up-to-date configuration changes, the FDM surrogates will confirm clearances and interfaces for installation assessment; highlight
serviceability issues; and validate routing interfaces
for wiring harnesses and fluid conduits. As the
product nears completion, the FDM surrogates may
also be used as a training aid for assembly
technicians or field service personnel.

FDM works by extruding small beads of
thermoplastic material through a nozzle that is
moved by a numerically controlled mechanism in
layers that harden immediately. The additive process
constructs surrogates in hours or days at a fraction
of the cost of production components. This lowers
acquisition cost and defers WIP expenses until final
assembly while shortening lead times to validate
installations.

When neighboring subassemblies are modified
or the surrogate reveals clearance issues, design
revisions are easily incorporated in subsequent
iterations since FDM requires no tooling.
New surrogates are conveniently produced to the
latest design revision. The thermoplastic surrogates
also offer the advantages of being lightweight
and non-marring. This makes installation easier
and reduces the possibility of damaging nearby
components or structures.

As efforts shift to final product assembly or
functional testing, FDM surrogates can highlight
the need for removal. Manufactured from colored
material— for example red—the surrogates
are visible to assembly technicians. Optionally,
embedded RFID sensors communicate the presence
of non-production components. Either option will
assure that all surrogates have been replaced with
the production parts they represent.

Process Overview

The configuration of FDM surrogates can be adjusted to match the immediate needs. For space claim
and assembly assessment, it is usually best to produce the subassembly to the final design. However, with
minor CAD adjustments, the FDM part can be simplified to include only areas of interest. If evaluating
interfaces of items such as fluid fittings, electrical connectors, air ducting or mounting surfaces, either
include them in the CAD model or attach production fittings to the FDM surrogate. For smart surrogates,
incorporate pockets in the model to accept RFID tags or sensors that will be embedded in the part. If
weight or balance is important when training installation and service technicians, add strategically placed
pockets in the CAD model that will be filled with ballast material.

“It takes a long time to design an aircraft. Starting from scratch it
can take five years, and it’s a rigorous development process to go
through,” says RP lab technician Mike Storp. “When using FDM
over the course of development for a new aircraft, there is great
potential to reduce costs and development time.”

Using FDM surrogates, conduits were ready for installation in two
and a half days. This is nearly a six-week reduction from Bell’s alternative, using cast aluminum parts. And
according to Storp, “We obviously saved money as well.”

As is often the case, the surrogates revealed needed design modification. According to Storp, “The
efficient process allows us to do more iterations than we could with other processes. That results in
better-designed components.”